Download PQ_Unit V

Unit V: Power Quality Monitoring
Monitoring considerations – Power line disturbance analyzer – Power quality measurement
equipment – Harmonic / spectrum analyzer – Flicker meters – Disturbance analyzer – Applications
of expert system for power quality monitoring
Part A
1. What are the power quality monitoring considerations?
 Monitoring to characterize system performance.
 Monitoring to characterize specific problems.
 Monitoring as part of an enhanced power quality service.
 Monitoring as part of predictive or just-in-time maintenance.
2. List the objectives of power quality measurements (Needs for power quality measurement).
 Preventive and predictive maintenance.
 Determining the need for mitigation equipment.
 Ensuring equipment performance.
 Sensitivity assessment of process equipment to disturbances.
3. Mention the three elements of power quality measurement.
There are three elements of power quality measurement, namely the measurement transducer, the
measurement unit and the evaluation unit.
4. What kind of power quality parameter do we want to measure?
Power quality includes a wide variety of conditions on the power system. Important disturbances
can vary in duration from very high-frequency impulses (lightning strokes) to long-term
overvoltages and interruptions. Standards, like IEC 61000 and EN 50160, and grid codes define
the power quality parameter to be measured. IEC 61000-4-30 defines the methods for
measurement and interpretation of results for power quality parameters in 50 Hz systems and is
part of the standard IEC 61000 of electromagnetic compatibility.
5. List the advantages of automatic power quality monitoring system.
 The power quality monitor allows engineers to take necessary or appropriate actions in a
timely manner.
 Advanced power quality monitors can be developed with integrated intelligent systems to
meet this new challenge.
 The system features on-the-spot data analysis with rapid information dissemination via
Internet technology, e-mails, pagers, and faxes.
6. Classify the power quality monitoring.
Local Monitoring: Its objective consists of determining the quality of power that is delivered to
a single customer.
System Monitoring: Its objective consists of determining the quality of power and the behavior
of the electrical system globally.
7. What are the basic categories of power quality instruments?
Basic categories of instruments that may be applicable include
 Wiring and grounding test devices
 Multimeters
 Oscilloscopes
 Disturbance analyzers
 Harmonic analyzers and spectrum analyzers
 Combination disturbance and harmonic analyzers
 Flicker meters
 Energy monitors
8. What is flicker meter?
Flicker meters measure flicker in terms of the fluctuating voltage magnitude and its
corresponding frequency of fluctuation. Electric arc furnaces and arc wielding usually cause
lights to flicker.
9. What is meant by power quality monitoring?
This is the process of collecting, analyzing and interpreting raw measurement data in to useful
information. The measurements can be compared and the level of power quality in the system can
be determined.
10. What are the specifications of power quality measuring equipments?
 The number of channels (for instance, single-phase or three-phase)
 The input voltage range
 The current measurement range
 Isolation
 Communication capabilities (For example, can the instrument be networked or tied to a standalone computer?)
11. What are the necessary measurements to be made to know about the power quality of a
product?
 Loose connections and overheating of conductors
 Magnetic field strength and electric field strength of conductors
 Static electricity of sensitive equipment
12. What is meant by online power quality monitoring?
On-line power quality data assessment analyzes data as they are captured. The analysis results
are available immediately for rapid dissemination. Complexity in the software design requirement for
on-line assessment is usually higher than that of off-line.
13. What is the need for FFT Spectrum analyzer in power quality analyzers?
a. They have the capability to measure both the voltage and current simultaneously so that
harmonic power flow information can be obtained.
b. They have the capability to measure both magnitude and phase angle of the individual
harmonic components.
c. Synchronization and a sampling rate fast enough to obtain accurate measurement of harmonic
components up to at least 37th harmonic.
d. They have the capability to characterize the statistical nature of harmonic distortion levels.
-----1. Explain the harmonic analyzer and disturbance analyzer. (16)
2. Write in detail about
a. Flicker meter
b. Application of expert system for power quality monitoring
3. With help of a block diagram, explain the applications of expert system for power quality
monitoring. (16)
4. Explain various power quality monitoring equipments. (16)
5. Discuss the factors to be considered in power quality monitoring. (8)